1. Field of the Invention
The present invention relates to an optical packet communication system using a wavelength-offset polarization-division multiplexing labeling. More particularly, the present invention relates to an optical packet communication system using a wavelength-offset polarization-division multiplexing labeling, which maintains a wavelength interval between packet data and a label constant to reduce a beating noise, thereby preventing deterioration of performance of an optical signal.
2. Description of the Related Art
In an optical packet switching network, each node includes an ingress node, a core node, and an egress node, wherein a sending end is positioned at the ingress node and a receiving end is positioned at the egress node. An optical signal is generated at the ingress node, and directly transmitted to the egress node. Otherwise, the optical signal is generated at the ingress node, and is transmitted to the egress node through the core node.
In such an optical packet switching network, packet data are transmitted together with a label. The label indicates information with respect to a moving direction of the packet data. How to assign the label is called a labeling. A labeled optical signal is generated at the ingress node and is transmitted to the core node. A label swapping device positioned at the core node determines a destination node of the optical signal, and transmits the optical signal to the determined node. A label swapping is an operation that substitutes a previous label by a new label at a core node that has received an optical signal from an ingress node, wherein the new label includes next moving direction information of the optical signal.
There are a time-division multiplexing (TDM) labeling, a wavelength-division multiplexing (WDM) labeling, an optical-code-division multiplexing (OCDM) labeling, a sub-carrier multiplexing (SCM) labeling, and an orthogonal optical labeling as examples of a labeling.
FIG. 1 is a view for illustrating a sub-carrier multiplexing labeling. With reference to FIG. 1, the sub-carrier multiplexing labeling has packet data containing information in the respective wavelengths λn (where, n is a natural number). A label is loaded at a position away from the respective waves by ±fc in a sub-carrier, and is transmitted with packet data. In such a sub-carrier multiplexing labeling, a label swapping device is very complicated, and it is thus difficult to embody the label swapping device.
Wavelength-division multiplexing is a technology that multiplexes and transmits optical channels having different wavelengths through one optical fiber. A wavelength-division multiplexing labeling transmits packet data at odd-numbered wavelengths λ2m+1 (m is a positive integer number), and loads and transmits a label at even-numbered wavelengths λ2m (m is a positive integer number). As discussed previously, since the wave-division multiplexing labeling loads and transmits label information at a wavelength different from that of the packet data, it requires an additional optical channel for labeling.
In accordance with a time-division multiplexing labeling, a label is assigned and transmitted between a first bit of packet data and an eighth bit of packet data. Accordingly, unlike the wave-division multiplexing labeling or the sub-carrier multiplexing labeling, in the time-division multiplexing labeling, in order to obtain label information, the packet data should be processed. This causes a label swapping process to be complicated.